The overall objectives of the research project are: To characterize established inherited growth disorders in mice and to determine their suitability as models for inherited growth disorders in human beings. To exploit these mutant mice to further our understanding of the function and control of both normal and abnormal growth processes. To utilize these models of inherited growth disorders to develop therapeutic treatments that will ameliorate the disease conditions in the mouse and by analogy prove fruitful for treatment of the human disorders. To search for and characterize new mutant genes in the mouse causing growth defects that are similar to known defects in human beings, thus providing additional animal models for investigation; and to make known and available to the scientific community present and future mutated genes of the mouse that affect growth processes. We are using the mouse as an animal model to investigate three inherited human disorders that affect growth: (1) familial panhypopituitarism, (2) isolated growth hormone deficiency type I, and (3) familial vitamin D resistant rickets. Mutant mice that are models for these inherited disorders are: (1) Snell's dwarf (dw/dw) and the Jackson dwarf (dwJ/dwJ), (2) little (lit/lit), and (3) hypophosphatemia (Hyp/Y or Hyp/+). BIBLIOGRAPHIC REFERENCES: Eicher, E.M., and W.G. Beamer. 1976. Inherited ateliotic dwarfism in mice: characteristics of the mutation, little, on Chromosome 6. J. Heredity 67:87-91. Beamer, W.G., and E.M. Eicher. 1976. Growth stimulation in little mice. J. Endocrinol. (in press).